Michael,
the behaviour of those frames is controlled by the geometry of the frame. That`s right. But what you measure is the behaviour of a resonating column of air. Please don't believe that both have the same length. All your horn simulations show that the influence of the horn contour does not stop immediately at the horn termination. Same for H, U, N ... frames. What you show in the green traces is quite naive compared to your horn sims IMHO.
You can do better for sure.
Rudolf
DFD / Deep Frame Dipole sub-woofer
sure I can look at those pipes as being horns, cavities, waveguides, diffraction alignment device, helmholtzresos or anything else - but I still don't get the point I'm afraid, with respect to superposition of dipole behaviour (green trace)
So - what you suggest in taking meaningful measurements ?- but keep in mind that I'm after optimization *not* after absolute accurate measurement - which is a fake under usual listening conditions anyway !
What is important is the trend and the underlaying principles.
So far I have not seen someone suggesting deep frame dipole sub's - have you?
Michael
sure I can look at those pipes as being horns, cavities, waveguides, diffraction alignment device, helmholtzresos or anything else - but I still don't get the point I'm afraid, with respect to superposition of dipole behaviour (green trace)
So - what you suggest in taking meaningful measurements ?
- but keep in mind that I'm after optimization *not* after absolute accurate measurement - which is a fake under usual listening conditions anyway !What is important is the trend and the underlaying principles.
So far I have not seen someone suggesting deep frame dipole sub's - have you?
Michael
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DFD / Deep Frame Dipole sub-woofer
Let us know, once you realize your ideas
Michael
Let us know, once you realize your ideas
Michael
DFD / Deep Frame Dipole sub-woofer
My guesstimate is it comes from reflections of the basket / magnet of the front chassis.
No idea - you have to find out by try and error, I'm afraid
Michael
My guesstimate is it comes from reflections of the basket / magnet of the front chassis.
No idea - you have to find out by try and error, I'm afraid
Michael
Michael,
I like your idea of taking nearfield measurements and superimposing them with a dipole "correction" to get an idea of the farfield response. That's a clever suggestion. Pity is your green curves are based on too simple assumptions IMHO - making the superposition results almost useless.
Rudolf
I like your idea of taking nearfield measurements and superimposing them with a dipole "correction" to get an idea of the farfield response. That's a clever suggestion. Pity is your green curves are based on too simple assumptions IMHO - making the superposition results almost useless.
I don't suggest new measurements. They are ok. They show what is to be expected.
I haven't either. But since I'm no longer interested in frames deeper than 20 cm, I have not looked for any "deep frame dipoles".So far I have not seen someone suggesting deep frame dipole sub's - have you?
Rudolf
DFD / Deep Frame Dipole sub-woofer
Ahh ok, at least we are talking about the same thing (was not sure about).
I agree on that my green trace for the inverse EQing is a "simplified assumption" - especially when it comes to higher frequencies due to directivity issues - but for the intended pass band and roughly one or two octaves above ???
That is why ?
Michael
Ahh ok, at least we are talking about the same thing (was not sure about).
I agree on that my green trace for the inverse EQing is a "simplified assumption" - especially when it comes to higher frequencies due to directivity issues - but for the intended pass band and roughly one or two octaves above ???
That is why ?
Michael
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My communication skills are at their worst when I presume there can't be a problem of mutual understanding.Ahh ok, at least we are talking about the same thing (was not sure about).
I agree on that my green trace for the inverse EQing is a "simplified assumption" - especially when it comes to higher frequencies due to directivity issues - but for the intended pass band and roughly one or two octaves above ???
Your H frame example shows the first dipole null at 420 Hz when it should be at ~310 Hz. That is "engineering thinking": Good enough for the application.
But I should not play the critic any longer. After taking some more time I find your combination of nearfield measurement and dipole interaction quite helpful for understanding something like the "ripole" response above the first peak for instance. I certainly have to withdraw that "almost useless" comment.
Well, I don't use dipoles as real subwoofers, but need an upper frequency limit of 300 Hz in my application. There is nothing wrong with DFD - they are just not part of my personal design goals.
Rudolf
BTW: How did you get the green dipole function into ARTA. Calculating with EXCEL and importing the SPL values?
After thinking along some more complicated lines first, I finally arrived at the point that with my PC setup its actually quite easy.
You just plug in an inverter VST followed by a delay you comfortably can dial in ms values, sum up with the original signal and you are done.
Green trace is a measurement of the sound card out in this configuration. Switching configurations is a breeze with Console.
Michael
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For the part above the Deep Frame Dipole sub's - roughly 100 up to 300Hz I use a 18" nude.
According to SL's spreadsheet this should be good enough for almost 120dB.
The part below 100Hz is the really tricky one with OB.
Stig Erik did it with sheer Sd - sadly I do not have the place nor the funds to follow his path.
So I was wondering what possibilities there are for optimization and still stay dipole.
Of course a Deep Frame Dipole sub woofer is a different animal compared to nude speakers - but on a first glance, it seems to blend pretty - as seem to do "normal" H-frame woofers
Michael
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Michael,You just plug in an inverter VST followed by a delay you comfortably can dial in ms values, sum up with the original signal and you are done.
Green trace is a measurement of the sound card out in this configuration. Switching configurations is a breeze with Console.
Thanks for explaining. I really need to look more into "designed" signals.
I am still "in clothes" - at least below the 300 Hz belt
: 15" in H frames 40x40x40 cmRudolf
DFD / Deep Frame Dipole sub-woofer
get undressed - at least up from the 100Hz belt !
I am still "in clothes" - at least below the 300 Hz belt
Rudolf
get undressed - at least up from the 100Hz belt !
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DFD / Deep Frame Dipole sub-woofer
Upper BW limit of an AMT sub - like my Deep Frame Dipole arrangement or the LAT / Transar is set by two factors - as easily can be seen by comparing my measurements above.
One limiting factor is the separation distance of the OB / framed OB - the second limiting factor is the pipe behaviour of a "pleat".
These are two completely different underlaying mechanisms we have to stay clear of.
Both mechanism superpose the well known comb filter effect above first peak.
As we usually would like to avoid the area above the first peak, this frequencies actually are the limiting factor (plus some margin).
As I have shown with making the "pleat" of conical shape we can up-shift at least the first peaking of the pipe at the same footprint - and thus extending the useful bandwidth.
Another way to up-shift first peak (due to dipole operation) is to lower separation distance - meaning - making a physically smaller speaker.
The trade off of small footprint AMT bass (like the LAT without additional baffle for example) is the loss of low frequency SPL, as also quite easily seen in my measurements above.
Michael
Upper BW limit of an AMT sub - like my Deep Frame Dipole arrangement or the LAT / Transar is set by two factors - as easily can be seen by comparing my measurements above.
One limiting factor is the separation distance of the OB / framed OB - the second limiting factor is the pipe behaviour of a "pleat".
These are two completely different underlaying mechanisms we have to stay clear of.
Both mechanism superpose the well known comb filter effect above first peak.
As we usually would like to avoid the area above the first peak, this frequencies actually are the limiting factor (plus some margin).
As I have shown with making the "pleat" of conical shape we can up-shift at least the first peaking of the pipe at the same footprint - and thus extending the useful bandwidth.
Another way to up-shift first peak (due to dipole operation) is to lower separation distance - meaning - making a physically smaller speaker.
The trade off of small footprint AMT bass (like the LAT without additional baffle for example) is the loss of low frequency SPL, as also quite easily seen in my measurements above.
Michael
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"I am trying to understand your last point about the HF bandwidth.
Is this because the plenum (which effectively acts as a low pass filter) is smaller and is now filtering less? "
"Because the magnets on the drivers limit how small you can make the "slots". "
The dimensions of the plenum determine the corner frequency of the low-pass filtering, primarily the depth. I think the tilt allows more on-axis SPL from the driver whose cone you can see. Electro-Voice made a speaker with one pair of 15s that was able to cross at 800hz to the HF horn. With some good 6-1/2s it should be possible to push it higher than this.
Madisound has some surplus Aurasound 6-1/2s for around $11 or so that look good. The T/S look suitable. They have paper cones and a neo magnet with a 1/2" thick top-plate with an underhung coil. The x-max at the 70% BL point looks to be about 4mm.
Is this because the plenum (which effectively acts as a low pass filter) is smaller and is now filtering less? "
"Because the magnets on the drivers limit how small you can make the "slots". "
The dimensions of the plenum determine the corner frequency of the low-pass filtering, primarily the depth. I think the tilt allows more on-axis SPL from the driver whose cone you can see. Electro-Voice made a speaker with one pair of 15s that was able to cross at 800hz to the HF horn. With some good 6-1/2s it should be possible to push it higher than this.
Madisound has some surplus Aurasound 6-1/2s for around $11 or so that look good. The T/S look suitable. They have paper cones and a neo magnet with a 1/2" thick top-plate with an underhung coil. The x-max at the 70% BL point looks to be about 4mm.
The "mass loading" saga of Ripols is mainly just that.
What looks as to be a down-shift in low cut is *mainly* a illusion caused by the SPL suck out towards higher frequencies.
Or in other words - we sadly do not gain anything - SPL wise. Maybe 1-2 dB at around 20Hz at best.
Ripole might be interesting for all-passive guys though, as it needs less EQing - despite the peak.
For optimization of SPL versus volume sadly its the wrong direction.
Michael
What looks as to be a down-shift in low cut is *mainly* a illusion caused by the SPL suck out towards higher frequencies.
Or in other words - we sadly do not gain anything - SPL wise. Maybe 1-2 dB at around 20Hz at best.
Ripole might be interesting for all-passive guys though, as it needs less EQing - despite the peak.
For optimization of SPL versus volume sadly its the wrong direction.
Michael
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